Karl Whitney's blog

A while ago I set myself the task of finding out what happens to our sewage once we flush the toilet. As a result, I spent much of the last 14 months thinking about sewage. I waded through the research and went to sewage plants and outfall pipes to have a nose around. The results of my investigations are in the Autumn issue of the Dublin Review:

When we think of sewage, we tend to think of human excrement. Drainage professionals use the term ‘wastewater’, and this is not a euphemism; it reflects the fact that most of what enters the sewer system is water: from showers, sinks, washing machines, dishwashers, toilets, industrial processes, and rain, which enters the drainage network via outdoor drains. But most of what makes wastewater offensive and dangerous, if it is not efficiently drained and treated, arises from the presence of human shit.

I outline the debate about the planned construction of a sewage plant in north Dublin and talk to some of those campaigning against the siting of the plant in their local area, including Loughshinny farmer Barry Rice:

One of the maps showed two green lines – the path of the proposed pipeline – leading towards an area of land north of the harbour. Here the lines joined a wide rectangular box whose borders were green and which was scored with diagonal lines, also green. The rectangular box stretched a couple of centimetres into the sea, while a small amount of land along the coast was also covered. This was the proposed area for the outfall sewer. Barry Rice looked at the map to see where his farm was located – ‘It’d be just kind of roughly … it’d be roughly along here, now. It’s obviously only a small bit of the coastline’ – and pointed to the land covered by the green box.

I wander around Ringsend sewage plant, the largest one in Ireland, with Michael Kenny, Acting Civil Engineer at the plant:

I was wearing a pair of safety glasses, a hard hat and a high-visibility jacket; although the possibility wasn’t discussed, I assumed the latter would be handy for locating me if I fell into a tank of sewage. I looked across the site of the plant, back towards the city. To my left, I could see Sandymount Strand curving southwards. Behind me, the open tanks of sewage bubbled through their treatment cycles. Beyond them, the imposing chimneys of the old Poolbeg power station reminded me that heights were relative. I took notes, juggling a pen and notebook and digital camera. Having my hands full in this way made me worry about dropping my pen into the sewage below.

A sequencing batch reactor tank at Ringsend sewage plant

I find a fairly disgusting pile of grit next to one of the tanks, and notice something disturbingly familiar there:

Whatever sinks to the base of the tank is spat out by two large plastic tubes into a long grey skip. Without getting any closer than was necessary, I had a look at the black-brown heaps of grit that had built up in the skip. There were stones there, as I’d expected, but the grit heaps were also dotted with a startling number of bright yellow specks that stood out against the dull background. It took me a second to realize what I was looking at.

‘You do get some organic stuff like sweetcorn,’ Kenny said.

I find out about the strange afterlife of sewage: how it’s converted to fertiliser and spread on fields, and give a brief history of Dublin’s subterranean sewage infrastructure. I also drag my girlfriend along to look at the largest sewage plant in Europe, near a small village to the west of Paris.